Major overheating problems...

[Kraig]

Got the car running finally. Installed a used 2002 motor, and a million other things. Everything needs to be replaced when a 1970 2002 sits indoors unused for 25 years.

Pulled the radiator, twice. Sent it to a reputable radiator shop, who cleaned and refurbished it. Replaced the thermostat, also twice. All new hoses. Coolant is passing through everywhere, all hoses get warm, so I don't think there's a blockage. Heater blows warm air.

Takes about 15 min of driving before gauge gets into the red, and then only about 10 min to cool down into the normal zone. Then it overheats again within 7 min.

What can the problem be? Would an air pocket in the system cause this?

[ROYinGA]

BMW. They have a vent bleeder screw though. Are you sure the thermostat is good. Put it in a pan of boiling water with a thermometer and make sure it is working OK.

[Kraig]

Vent bleeder screw? Where is this located? Thermostat is good, have gone through two of them. Water pump is also new, radiator has been cleaned out, and flows as it should.

[jonblbl]

Couple quick thoughts:

My personal experience and inputs from posts about overheating are that the stock radiator will not do the job. I replaced it with a 320 radiator, which works better, but does overheat under extreme conditions (90 degrees idling in traffic).

Are you sure the temp gauge is accurate? The gauge may read high. Does the engine continue to run smooth when in the red? Rough idle is a definite overheating sign.

[Kraig]

I just can't beleive that the radiator would allow it to overheat after just 15 min of normal driving in 70 degree weather. Temp gauge seems to work fine. I can't even drive the car for a few blocks!

I would definitely suspect the radiator if it overheated in certain circumstances. But all the time? No matter the weather or traffic? That's beyond the radiator.

But thanks for your ideas!

[jonblbl]

Do an overheating 'search' on this site. Also on 2002FAQ.

I recall some other causes, like timing and head gasket. You can try the easy stuff first to zero in on the culprit.

[Arizona 02]

[Arizona 02]

from system put the front end of car up on jack stands, heater valve open to allow coolant to flow through the heater core pushing air out,idle motor w/ cap off.After t/stat has has been open a few minutes then your done.If you see a constant supply of air bubbles that can indicate head gasket problem.
With the rad cap off & the fluid level low, look inside the rad at the tubes to see if small debris has collected in the tube opening= clogging the radiator.The debris became dislodge from the inner passages of the block & head. Frustrating after having the rad cleaned out.
Was the block drain plug removed (exhaust side @ # 4 cyl area) to flushed out the engine.

[ROYinGA]

[Ole1.6]

I have a '67 1600 that had a cracked head (creamy oil) when I found it. I replaced the head first, flushed the block and heater core many times. Lotsa rusty water! Rodded (or rotted) the radiator. The bugger still overheated. Replaced the hoses and thermostat. Still ran in the red and I would have to shut down. During the extended running and flushing, alot of scale broke free from the block and I had to get the radiator done again. Finally the water ran clear and it started to cool only slightly so I started to run antifreez. During the repeated flushes I discovered how to burp the car. Turn the heater valve on and squeeze the lower hose until water gurgles in and run until you feel hot water top and bottom hoses.
I found 2 major problems were causing my repeated visits to the red zone.
1. There was a large chunk rusty matter lodged in the heater hose that exited the rear of the head!!!! I don't know how long it was there but when I removed it that was a big step. I still had more to go. I had a triple core installed and the bigger 5 blade fan to replace the smaller 4 blade. This did not improve too much.
2. The last item that brought me into normal temp zone, even in hot weather, was adjust my timing!!!
I tried not to run the car in the red for too long during the proccess. Good luck.